1. Field of the Invention
This invention relates generally to an elevated temperature forming die apparatus for fabrication of deep draw panels such as door inners from workpieces with limited formability such as aluminum or magnesium sheet material.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Elevated temperature forming methods and die apparatus are known in the art. For example, U.S. Pat. No. 7,159,437 issued 9 Jan. 2007 to Schroth, et al., discloses an elevated temperature forming method and a die apparatus that includes a hot forming tool including a die set comprising a lower die part having a forming surface shaped complementary to a desired shape of a portion of the metal sheet workpiece and an upper die part supported for reciprocal motion relative to the lower die part along a die set stroke extending between open and closed die set positions and having a forming surface shaped complementary to a desired shape of a portion of the workpiece such that relative movement of the upper and lower die parts to the closed die set position imparts a desired shape to a portion of a workpiece positioned between the upper and lower die parts. The Schroth patent also discloses multiple electrical resistance cartridge heaters carried by the upper and lower die parts and positioned using numerical thermal finite element and optimization analysis such that when each heating element is simultaneously powered on for an identical fraction of the time an acceptable temperature distribution will be produced within the tool such that entire forming surfaces of the upper and lower die parts are maintained within a predetermined temperature range. Also disclosed in the Schroth patent is a temperature controller comprising a power controller connected to the cartridge heaters carried by the lower die part and programmed to maintain the forming surface of the lower die part within the predetermined temperature range by controlling power application to the cartridge heaters carried by the lower die part. The Schroth temperature controller also discloses including a second power controller connected to the cartridge heaters carried by the upper die part and programmed to maintain the forming surface of the upper die part within the predetermined temperature range by controlling power application to the cartridge heaters carried by the upper die part. However, the Schroth patent doesn't contemplate the controlled drawing of sheet material workpieces.
What would be desirable would be an elevated temperature forming die apparatus capable of fabricating deep drawn panels such as door inners from sheet workpieces comprising materials of limited formability.